It is well known that vinyl resins may be plasticized or changed from the hard, horny and stiff state to a soft, plastic workable condition by the addition thereto of certain plasticizers, such as dioctyl phthalate, and the like. These vinyl polymers or resins are referred to as dispersion resins or paste resins and are usually made employing an emulsion polymerization technique. When a vinyl resin is mixed or blended with a plasticizer, it is referred to as a "plastisol". By virtue of the flowability of the plastisol, it can be processed into various useful products. Plastisols can be used in making molded products, coatings, and the like. Accordingly, the dispersion resin must be capable of being mixed with a plasticizer easily and uniformly to form low viscosity plastisols which are stable, containing particles of uniform and proper size, and capable of producing films and like products, of good clarity.
The vinyl copolymers made by emulsion polymerization are very useful in making plastisols for extruded products, films, and the like. When making vinyl copolymers by emulsion polymerization, one cannot get enough comonomer into the polymer to get the desired results in the plastisol, such as low fusion temperature in the plastisol. Increasing the concentration of comonomer results in increasing plastisol viscosity. When enough comonomer is incorporated in the copolymer to give the desired low fusion temperature, it often becomes impossible to make a fluid dispersion of the copolymer in the plasticizer at practical ratios.
A most important problem today is the increasing cost of energy. As a result, there is a great need in the marketplace for a low-energy vinyl copolymer or resin. By low energy vinyl copolymer is meant one that can be processed either at a lower temperature or at a faster speed as compared to those vinyl copolymers currently available. This is particularly important in the case of the dispersion vinyl copolymers where a large amount of heat is needed to fuse the plastisols made therefrom. Therefore, there is a need in the art for a method of making low fusion dispersion vinyl copolymers which result in improved plastisol properties.